47 research outputs found
Distributed communications in collision channels with errors
Analysis of distributed communication networks in noisy collision channels is given. Both feedback and feedforward channel errors are considered. A finite number of buffered users is addressed. It is shown that channel errors lead to stabilization of unstable access protocols, i.e. to elimination of the saturation phenomena and to stabilization of a network in a unique, globally asymptotically stable steady state with relatively high-performance characteristics. Thus channel noise, possibly introduced intentionally, could be viewed as a decentralized stabilizing controller.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26161/1/0000238.pd
How wireless queues benefit from motion: an analysis of the continuum between zero and infinite mobility
This paper considers the time evolution of a queue that is embedded in a
Poisson point process of moving wireless interferers. The queue is driven by an
external arrival process and is subject to a time-varying service process that
is a function of the SINR that it sees. Static configurations of interferers
result in an infinite queue workload with positive probability. In contrast, a
generic stability condition is established for the queue in the case where
interferers possess any non-zero mobility that results in displacements that
are both independent across interferers and oblivious to interferer positions.
The proof leverages the mixing property of the Poisson point process. The
effect of an increase in mobility on queueing metrics is also studied. Convex
ordering tools are used to establish that faster moving interferers result in a
queue workload that is smaller for the increasing-convex stochastic order. As a
corollary, mean workload and mean delay decrease as network mobility increases.
This stochastic ordering as a function of mobility is explained by establishing
positive correlations between SINR level-crossing events at different time
points, and by determining the autocorrelation function for interference and
observing that it decreases with increasing mobility. System behaviour is
empirically analyzed using discrete-event simulation and the performance of
various mobility models is evaluated using heavy-traffic approximations.Comment: Preliminary version appeared in WiOPT 2020. New version with
revision
Robust and Listening-Efficient Contention Resolution
This paper shows how to achieve contention resolution on a shared
communication channel using only a small number of channel accesses -- both for
listening and sending -- and the resulting algorithm is resistant to
adversarial noise.
The shared channel operates over a sequence of synchronized time slots, and
in any slot agents may attempt to broadcast a packet. An agent's broadcast
succeeds if no other agent broadcasts during that slot. If two or more agents
broadcast in the same slot, then the broadcasts collide and both broadcasts
fail. An agent listening on the channel during a slot receives ternary
feedback, learning whether that slot had silence, a successful broadcast, or a
collision. Agents are (adversarially) injected into the system over time. The
goal is to coordinate the agents so that each is able to successfully broadcast
its packet.
A contention-resolution protocol is measured both in terms of its throughput
and the number of slots during which an agent broadcasts or listens. Most prior
work assumes that listening is free and only tries to minimize the number of
broadcasts.
This paper answers two foundational questions. First, is constant throughput
achievable when using polylogarithmic channel accesses per agent, both for
listening and broadcasting? Second, is constant throughput still achievable
when an adversary jams some slots by broadcasting noise in them? Specifically,
for packets arriving over time and jammed slots, we give an algorithm
that with high probability in guarantees throughput and
achieves on average channel accesses against an
adaptive adversary. We also have per-agent high-probability guarantees on the
number of channel accesses -- either or , depending on how quickly the adversary can react to what
is being broadcast
Multi-user resource-sharing problem for the Internet
In this thesis we study a series of multi-user resource-sharing problems for the Internet, which involve distribution of a common resource among participants of multi-user systems (servers or networks). We study concurrently accessible resources, which for end-users may be exclusively accessible or non-exclusively. For all kinds we suggest a separate algorithm or a modification of common reputation scheme. Every algorithm or method is studied from different perspectives: optimality of protocols, selfishness of end users, fairness of the protocol for end users. On the one hand the multifaceted analysis allows us to select the most suited protocols among a set of various available ones based on trade-offs of optima criteria. On the other hand, the future Internet predictions dictate new rules for the optimality we should take into account and new properties of the networks that cannot be neglected anymore.
In this thesis we have studied new protocols for such resource-sharing problems as the backoff protocol, defense mechanisms against Denial-of-Service, fairness and confidentiality for users in overlay networks. For backoff protocol we present analysis of a general backoff scheme, where an optimization is applied to a general-view backoff function. It leads to an optimality condition for backoff protocols in both slot times and continuous time models. Additionally we present an extension for the backoff scheme in order to achieve fairness for the participants in an unfair environment, such as wireless signal strengths. Finally, for the backoff algorithm we suggest a reputation scheme that deals with misbehaving nodes. For the next problem -- denial-of-service attacks, we suggest two schemes that deal with the malicious behavior for two conditions: forged identities and unspoofed identities. For the first one we suggest a novel most-knocked-first-served algorithm, while for the latter we apply a reputation mechanism in order to restrict resource access for misbehaving nodes. Finally, we study the reputation scheme for the overlays and peer-to-peer networks, where resource is not placed on a common station, but spread across the network. The theoretical analysis suggests what behavior will be selected by the end station under such a reputation mechanism.Tässä väitöskirjassa tutkimme useita Internetin resurssienjako-ongelmia,
jotka liittyvät yhteisten resurssien käyttöön ja jakamiseen monen
käyttäjän järjestelmissä. Tutkimme rinnakkain käytettäviä resursseja,
jotka voidaan antaa käyttäjille omaan tai jaettuun käyttöön. Ratkaisuna
ehdotamme joko uutta algoritmia tai muutoksia olemassaoleviin
tunnettuihin mainejärjestelmiin. Kaikkia algoritmeja tutkitaan
useammasta näkökulmasta: protokollien optimaalisuus, käyttäjien
itsekkyys, protokollan reiluus käytäjiä kohtaan. Tämä monikantainen
analyysi mahdollistaa sopivimman protokollan valinnan, ottaen huomioon
erilaiset optimointikriteerit. Toisaalta, tulevaisuuden verkkoratkaisut
määrittelevät uusia optimointisääntöjä, sekä verkkojen uusia
ominaisuuksia, jotka molemmat pitää ottaa tulevaisuudessa huomioon